The offensive, which involved at least 2,000 ground troops and 10 F-16 warplanes, underscores a growing cycle of violence in the mainly Kurdish southeast of the country - a development Turkish leaders have linked to the nearby conflict in Syria.

"Around 2,000 soldiers are involved in the operation. Cobra helicopters ... are bombing targets on the Kato mountain," a security source told Reuters, referring to a location in south-eastern Sirnak province, which borders Iraq and Syria.

Up to 10 F-16 fighter jets had also been sent from a nearby base in Diyarbakir to support the operation, the source said. At least one soldier was killed and two wounded as the first clashes started with ground troops.

There were no reports that Turkish ground troops had crossed the border, although Turkey has sent soldiers into the region in the past.

Residents across the border in northern Iraq, from where the outlawed Kurdistan Workers Party (PKK) commands its operations against the Turkish state, said warplanes had also bombed the remote area of Dwele inside Iraq but there were no immediate reports of casualties.

Officials from the semi-autonomous Kurdistan Regional Government (KRG) did not immediately answer calls seeking comment.

Turkey has stepped up air operations on suspected PKK rebels in northern Iraq over the past year after an increase in PKK attacks. The raids have fuelled tension between Ankara and the KRG.

The Turkish assault comes days after PKK fighters killed 10 members of Turkey's security services in simultaneous attacks on four state and security installations in Sirnak. ID:nL6E8K301Q]

Turkey has seen some of the fiercest fighting this summer between PKK rebels and Turkish security forces since the separatist militants took up arms in 1984 with the aim of carving out their own state in the southeast.

The PKK, which is considered a terrorist organisation by Turkey, the United States and the European Union, has since scaled back their demands to greater Kurdish autonomy.

More than 40,000 people have been killed since the start of the conflict.

Ankara has increasingly blamed the rise in violence within its own borders on the unrest in Syria and Prime Minister Tayyip Erdogan has accused Syria's President Bashar al-Assad of arming the PKK militants.

Turkey has raised the possibility of military intervention in Syria if the PKK were to launch attacks from Syrian soil and on Wednesday, the military conducted a major military exercise on the Syrian border, a clear warning to Damascus.